A Three-Dimensional Azo-Bridged Porous Porphyrin Framework Supported Silver Nanoparticles as the State-of-the-Art Catalyst for the Carboxylative Cyclization of Propargylic Alcohols with CO2 under Ambient Conditions

Abstract

Designing efficient heterogeneous catalysts for the atmospheric fixation of CO₂ at room temperature remains a formidable challenge due to their high thermodynamic stability and kinetic inertness. Herein, a versatile nanocomposite of Aza-Por-TAPM-immobilized silver nanoparticles (AgNPs), Ag/Azo-Por-TAPM, has been successfully fabricated by adopting a three-dimensional azo-bridged porous porphyrin framework (Azo-Por-TAPM) as the porous support through a simple “liquid impregnation and in situ reduction” strategy. After adjusting the chemical structure of the porphyrin framework, the experimental results reveal that the presence of abundant azo groups and distorted tetrahedral structures is conducive to the preparation of highly dispersed and small-sized AgNPs at its surface. Further studies discover that Ag/Azo-Por-TAPM exhibits a record-level catalytic activity in the carboxylative cyclization of propargylic alcohols with CO₂ at room temperature, achieving maximum turnover frequencies of 4600 h^–1 at 10 bar and 1050 h^–1 at 1 bar, which far exceed that of the previously reported catalysts. In addition, Ag/Aza-Por-TAPM has a high catalytic efficiency with simulated industrial fuel gas under ambient conditions and can be easily recovered and reused at least six times without a significant decrease in catalytic activity. The significantly reduced activation energy, together with the analytical results of NMR spectra, demonstrate that AgNPs-driven alkyne activation is considered as the rate-determining step of the cyclization reaction. This work not only reports a kind of porous porphyrin polymers loaded AgNPs for mild CO₂ conversion but also brings some inspiration to designing highly efficient catalysts for the integration of CO₂ capture and utilization.